1. Field of the Invention
The present invention relates to a portable wireless terminal, and more particularly to a folder type terminal, in which grounds formed in a main body and in a folder are electrically connected to each other, so that an amount of electromagnetic wave absorptance to which a user is exposed can be reduced.
2. Description of the Related Art
In general, portable wireless terminals can be divided into three types according to external form: bar type terminals, flip type terminals, and folder type terminals.
The bar type terminal has a data input/output means and a transmitter/receiver module mounted in one main housing. In the bar type terminal, mistaken operation can occur because a keypad as data input means is always exposed to the outside. Also, its miniaturization is limited because a minimum distance must be maintained between the transmitter part and the receiver part.
The flip type terminal is comprised of a main body, a flip, and a hinge device connecting the flip to the main body. An input/output means and a transmitter/receiver module are mounted in the main body. In the flip type terminal, mistaken operation as in the bar type terminal may be prevented because the flip covers a keypad as data input means. However, the flip type terminal has the same limitation on its miniaturization as described above for the bar type terminal, and for similar reasons.
The folder type terminal comprises a main body, a folder, and a hinge device pivotably connecting the folder to the main body. The folder is opened and shut by a pivot movement of the folder. When the folder is in close contact with the main body, that is, in a stand-by mode, the folder covers a keypad, and thus mistaken operation as described with reference to the bar type terminal can be prevented. Further, a folder type terminal can be miniaturized more than a bar type or flip type terminal and still maintain a sufficient distance between the transmitter part and the receiver part in a call mode.
FIG. 1 is a perspective view of a conventional portable wireless terminal, in particular, a conventional folder type terminal 100.
As shown in FIG. 1, the conventional folder type terminal comprises a main body 110 and a folder 150 which is connected to the main body 110 in such a manner that it can be opened and shut by being pivoted on the hinge device (not shown).
In the main body 110, a keypad 113 and a transmitter part 115 are provided on the housing 111, and a side hinge arm 117 is disposed on each of both upper sides of the housing 111.
In the folder 150, a display device 153 is exposed on a housing 151, and a receiver part 155 is provided in an upper portion of the housing 151. A center hinge arm 157, which is interposed between the side hinge arms 117 of the main body housing 110, is also disposed in a lower portion of the folder housing 151 to pivotably connect the folder 150 to the main body 110. The designated hinge device is installed in the center hinge arm 157.
The conventional hinge device of FIG. 1 is disclosed in U.S. Pat. No. 6,292,980 which is commonly assigned to the assignee of the present invention. The disclosed hinge device has a hinge cam and a hinge shaft which are formed with a mountain-shaped portion and a valley-shaped portion, respectively, and a coil spring which brings the hinge cam in close contact with the hinge shaft. Because the hinge device accommodates the hinge cam, the hinge shaft and the coil spring in a hinge housing, curved surfaces of the mountain-shaped portion and the valley-shaped portion and a resilient force of the coil spring maintain connection during the opening and closing of the folder or the flip.
Many countries of the world are tightening control over electromagnetic wave emissions in accordance with published study results showing that electromagnetic waves may be harmful to the human body.
Measures to reduce electromagnetic wave emissions of portable wireless terminals are limited, in practice, to attaching an electromagnetic wave absorber to an antenna or an antenna part to which electric current is supplied, or changing a ground pattern formed inside an injection molding material of the terminal to either shift a position in which the electromagnetic are concentrated or compensate for the concentrated electromagnetic waves. Moreover, such measures may be available for reducing an electromagnetic wave absorptance of a human body, but they give rise to a disadvantageous lowering of the radiation characteristics of an antenna. In order to simultaneously respect the electromagnetic wave absorptance limitation of the human body and maintain the radiation characteristics of an antenna, a position of an electromagnetic wave absorber or a ground pattern must be changed only by repeated tests and verifications. There is another problem in that use of metallic components in the hinge device of a folder type terminal degrades the operational characteristics of the terminal, such as the radiation characteristics of an antenna.